This invention relates to foot operated swimming aids, and more particularly to improved swim fins for attachment to individual feet or monofins for attachment to both feet. Swim fins of many different shapes and operating features have been invented in an attempt to increase the propulsion effeciency of a swimmer's leg action. U.S. Pat. No. 3,055,025 issued Sep. 25, 1962 to Ferraro presents a vector analysis demonstrating how certain portions of the stroke actually push the swimmer backward with conventional swim fins. U.S. Pat. Nos. 5,597,336; 4,929,206; 5,356,323; and 5,429,536 issued to Evans disclose fin blades with lateral elements that bend toward each other for enhanced efficiency. U.S. Pat. No. 4,664,639 issued May 12, 1987 to Schneider teaches a foot fin with a foil or flap hinged to the forward part of the shoe and extending backward therefrom. There is reduced resistance in moving the foot forward and increased resistance in moving the foot backward. It is employed with the user floating upright in a walking motion. U.S. Pat. No. 2,343,468 issued Mar. 7, 1944 to Messinger teaches a foil attached pivotally to the toe and extending outward therefrom. U.S. Pat. No. 3,178,738 issued Apr. 20, 1965 to La Trell teaches a fin that fastens to a shoe. Continued attempts to improve the efficiency of swim fins indicates that a need still exists for improvements in the art so that the strength of the human leg muscles may be more effectively employed for aquatic propulsion.